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Linux/net/bridge/br_input.c

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  1 /*
  2  *      Handle incoming frames
  3  *      Linux ethernet bridge
  4  *
  5  *      Authors:
  6  *      Lennert Buytenhek               <buytenh@gnu.org>
  7  *
  8  *      This program is free software; you can redistribute it and/or
  9  *      modify it under the terms of the GNU General Public License
 10  *      as published by the Free Software Foundation; either version
 11  *      2 of the License, or (at your option) any later version.
 12  */
 13 
 14 #include <linux/slab.h>
 15 #include <linux/kernel.h>
 16 #include <linux/netdevice.h>
 17 #include <linux/etherdevice.h>
 18 #include <linux/netfilter_bridge.h>
 19 #include <linux/neighbour.h>
 20 #include <net/arp.h>
 21 #include <linux/export.h>
 22 #include <linux/rculist.h>
 23 #include "br_private.h"
 24 
 25 /* Hook for brouter */
 26 br_should_route_hook_t __rcu *br_should_route_hook __read_mostly;
 27 EXPORT_SYMBOL(br_should_route_hook);
 28 
 29 static int
 30 br_netif_receive_skb(struct net *net, struct sock *sk, struct sk_buff *skb)
 31 {
 32         return netif_receive_skb(skb);
 33 }
 34 
 35 static int br_pass_frame_up(struct sk_buff *skb)
 36 {
 37         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
 38         struct net_bridge *br = netdev_priv(brdev);
 39         struct net_bridge_vlan_group *vg;
 40         struct pcpu_sw_netstats *brstats = this_cpu_ptr(br->stats);
 41 
 42         u64_stats_update_begin(&brstats->syncp);
 43         brstats->rx_packets++;
 44         brstats->rx_bytes += skb->len;
 45         u64_stats_update_end(&brstats->syncp);
 46 
 47         vg = br_vlan_group_rcu(br);
 48         /* Bridge is just like any other port.  Make sure the
 49          * packet is allowed except in promisc modue when someone
 50          * may be running packet capture.
 51          */
 52         if (!(brdev->flags & IFF_PROMISC) &&
 53             !br_allowed_egress(vg, skb)) {
 54                 kfree_skb(skb);
 55                 return NET_RX_DROP;
 56         }
 57 
 58         indev = skb->dev;
 59         skb->dev = brdev;
 60         skb = br_handle_vlan(br, vg, skb);
 61         if (!skb)
 62                 return NET_RX_DROP;
 63         /* update the multicast stats if the packet is IGMP/MLD */
 64         br_multicast_count(br, NULL, skb, br_multicast_igmp_type(skb),
 65                            BR_MCAST_DIR_TX);
 66 
 67         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN,
 68                        dev_net(indev), NULL, skb, indev, NULL,
 69                        br_netif_receive_skb);
 70 }
 71 
 72 static void br_do_proxy_arp(struct sk_buff *skb, struct net_bridge *br,
 73                             u16 vid, struct net_bridge_port *p)
 74 {
 75         struct net_device *dev = br->dev;
 76         struct neighbour *n;
 77         struct arphdr *parp;
 78         u8 *arpptr, *sha;
 79         __be32 sip, tip;
 80 
 81         BR_INPUT_SKB_CB(skb)->proxyarp_replied = false;
 82 
 83         if ((dev->flags & IFF_NOARP) ||
 84             !pskb_may_pull(skb, arp_hdr_len(dev)))
 85                 return;
 86 
 87         parp = arp_hdr(skb);
 88 
 89         if (parp->ar_pro != htons(ETH_P_IP) ||
 90             parp->ar_op != htons(ARPOP_REQUEST) ||
 91             parp->ar_hln != dev->addr_len ||
 92             parp->ar_pln != 4)
 93                 return;
 94 
 95         arpptr = (u8 *)parp + sizeof(struct arphdr);
 96         sha = arpptr;
 97         arpptr += dev->addr_len;        /* sha */
 98         memcpy(&sip, arpptr, sizeof(sip));
 99         arpptr += sizeof(sip);
100         arpptr += dev->addr_len;        /* tha */
101         memcpy(&tip, arpptr, sizeof(tip));
102 
103         if (ipv4_is_loopback(tip) ||
104             ipv4_is_multicast(tip))
105                 return;
106 
107         n = neigh_lookup(&arp_tbl, &tip, dev);
108         if (n) {
109                 struct net_bridge_fdb_entry *f;
110 
111                 if (!(n->nud_state & NUD_VALID)) {
112                         neigh_release(n);
113                         return;
114                 }
115 
116                 f = __br_fdb_get(br, n->ha, vid);
117                 if (f && ((p->flags & BR_PROXYARP) ||
118                           (f->dst && (f->dst->flags & BR_PROXYARP_WIFI)))) {
119                         arp_send(ARPOP_REPLY, ETH_P_ARP, sip, skb->dev, tip,
120                                  sha, n->ha, sha);
121                         BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
122                 }
123 
124                 neigh_release(n);
125         }
126 }
127 
128 /* note: already called with rcu_read_lock */
129 int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
130 {
131         bool local_rcv = false, mcast_hit = false, unicast = true;
132         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
133         const unsigned char *dest = eth_hdr(skb)->h_dest;
134         struct net_bridge_fdb_entry *dst = NULL;
135         struct net_bridge_mdb_entry *mdst;
136         struct net_bridge *br;
137         u16 vid = 0;
138 
139         if (!p || p->state == BR_STATE_DISABLED)
140                 goto drop;
141 
142         if (!br_allowed_ingress(p->br, nbp_vlan_group_rcu(p), skb, &vid))
143                 goto out;
144 
145         /* insert into forwarding database after filtering to avoid spoofing */
146         br = p->br;
147         if (p->flags & BR_LEARNING)
148                 br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
149 
150         if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
151             br_multicast_rcv(br, p, skb, vid))
152                 goto drop;
153 
154         if (p->state == BR_STATE_LEARNING)
155                 goto drop;
156 
157         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
158 
159         local_rcv = !!(br->dev->flags & IFF_PROMISC);
160 
161         if (IS_ENABLED(CONFIG_INET) && skb->protocol == htons(ETH_P_ARP))
162                 br_do_proxy_arp(skb, br, vid, p);
163 
164         if (is_broadcast_ether_addr(dest)) {
165                 local_rcv = true;
166                 unicast = false;
167         } else if (is_multicast_ether_addr(dest)) {
168                 mdst = br_mdb_get(br, skb, vid);
169                 if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
170                     br_multicast_querier_exists(br, eth_hdr(skb))) {
171                         if ((mdst && mdst->mglist) ||
172                             br_multicast_is_router(br)) {
173                                 local_rcv = true;
174                                 br->dev->stats.multicast++;
175                         }
176                         mcast_hit = true;
177                 } else {
178                         local_rcv = true;
179                         br->dev->stats.multicast++;
180                 }
181                 unicast = false;
182         } else if ((dst = __br_fdb_get(br, dest, vid)) && dst->is_local) {
183                 /* Do not forward the packet since it's local. */
184                 return br_pass_frame_up(skb);
185         }
186 
187         if (dst) {
188                 dst->used = jiffies;
189                 br_forward(dst->dst, skb, local_rcv, false);
190         } else {
191                 if (!mcast_hit)
192                         br_flood(br, skb, unicast, local_rcv, false);
193                 else
194                         br_multicast_flood(mdst, skb, local_rcv, false);
195         }
196 
197         if (local_rcv)
198                 return br_pass_frame_up(skb);
199 
200 out:
201         return 0;
202 drop:
203         kfree_skb(skb);
204         goto out;
205 }
206 EXPORT_SYMBOL_GPL(br_handle_frame_finish);
207 
208 static void __br_handle_local_finish(struct sk_buff *skb)
209 {
210         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
211         u16 vid = 0;
212 
213         /* check if vlan is allowed, to avoid spoofing */
214         if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
215                 br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
216 }
217 
218 /* note: already called with rcu_read_lock */
219 static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
220 {
221         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
222 
223         __br_handle_local_finish(skb);
224 
225         BR_INPUT_SKB_CB(skb)->brdev = p->br->dev;
226         br_pass_frame_up(skb);
227         return 0;
228 }
229 
230 /*
231  * Return NULL if skb is handled
232  * note: already called with rcu_read_lock
233  */
234 rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
235 {
236         struct net_bridge_port *p;
237         struct sk_buff *skb = *pskb;
238         const unsigned char *dest = eth_hdr(skb)->h_dest;
239         br_should_route_hook_t *rhook;
240 
241         if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
242                 return RX_HANDLER_PASS;
243 
244         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
245                 goto drop;
246 
247         skb = skb_share_check(skb, GFP_ATOMIC);
248         if (!skb)
249                 return RX_HANDLER_CONSUMED;
250 
251         p = br_port_get_rcu(skb->dev);
252 
253         if (unlikely(is_link_local_ether_addr(dest))) {
254                 u16 fwd_mask = p->br->group_fwd_mask_required;
255 
256                 /*
257                  * See IEEE 802.1D Table 7-10 Reserved addresses
258                  *
259                  * Assignment                           Value
260                  * Bridge Group Address         01-80-C2-00-00-00
261                  * (MAC Control) 802.3          01-80-C2-00-00-01
262                  * (Link Aggregation) 802.3     01-80-C2-00-00-02
263                  * 802.1X PAE address           01-80-C2-00-00-03
264                  *
265                  * 802.1AB LLDP                 01-80-C2-00-00-0E
266                  *
267                  * Others reserved for future standardization
268                  */
269                 switch (dest[5]) {
270                 case 0x00:      /* Bridge Group Address */
271                         /* If STP is turned off,
272                            then must forward to keep loop detection */
273                         if (p->br->stp_enabled == BR_NO_STP ||
274                             fwd_mask & (1u << dest[5]))
275                                 goto forward;
276                         *pskb = skb;
277                         __br_handle_local_finish(skb);
278                         return RX_HANDLER_PASS;
279 
280                 case 0x01:      /* IEEE MAC (Pause) */
281                         goto drop;
282 
283                 case 0x0E:      /* 802.1AB LLDP */
284                         fwd_mask |= p->br->group_fwd_mask;
285                         if (fwd_mask & (1u << dest[5]))
286                                 goto forward;
287                         *pskb = skb;
288                         __br_handle_local_finish(skb);
289                         return RX_HANDLER_PASS;
290 
291                 default:
292                         /* Allow selective forwarding for most other protocols */
293                         fwd_mask |= p->br->group_fwd_mask;
294                         if (fwd_mask & (1u << dest[5]))
295                                 goto forward;
296                 }
297 
298                 /* Deliver packet to local host only */
299                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, dev_net(skb->dev),
300                         NULL, skb, skb->dev, NULL, br_handle_local_finish);
301                 return RX_HANDLER_CONSUMED;
302         }
303 
304 forward:
305         switch (p->state) {
306         case BR_STATE_FORWARDING:
307                 rhook = rcu_dereference(br_should_route_hook);
308                 if (rhook) {
309                         if ((*rhook)(skb)) {
310                                 *pskb = skb;
311                                 return RX_HANDLER_PASS;
312                         }
313                         dest = eth_hdr(skb)->h_dest;
314                 }
315                 /* fall through */
316         case BR_STATE_LEARNING:
317                 if (ether_addr_equal(p->br->dev->dev_addr, dest))
318                         skb->pkt_type = PACKET_HOST;
319 
320                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING,
321                         dev_net(skb->dev), NULL, skb, skb->dev, NULL,
322                         br_handle_frame_finish);
323                 break;
324         default:
325 drop:
326                 kfree_skb(skb);
327         }
328         return RX_HANDLER_CONSUMED;
329 }
330 

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